Safety control and ignition system



atenied ec. 25, 1945 2,391,153 SAFETY CONTROL AND IGNITION SYSTEM Charles K. Strobel, Pittsburgh, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application May 4, 1945, Serial No. 591,959

'I Claims.

This invention relates to safety control and ignition systems for gaseous fuel burners and. more particularly, to electrical systems therefor.

In apparatus of this general character the flow of fuel to the main burner may be controlled by an electromagnetic control device which is energized by the current generated by a thermocouple or thermopile responsive to the heat of a flame at the pilot burner. Means are employed for placing the armature of the electromagnet in attracted position and the fuel control device in a now permitting position, such operation being generally termed resetting The means employed for resetting may be electrically operated from a source of current separate from that generated bythe thermocouple. It is apparent that once the resetting operation is completed, the current from this separate source is no longer required and the electromagnetic control device may be left under the sole control of the thermoelectric current which is generated as long as the pilot burner produces a flame.

An object of this invention is to reset an electromagnetic device by electrically operated means which are rendered inoperative upon completion of the resetting operation.

Another object of the inventionis to eliminate unnecessary noise in a recycling control system having the electrically operated resetting means.

Another Object of the invention is to reduce the electrical energy from external sources required during the running period to a negligible value.

Another obj ect of the invention is to incorporate a purge period in the recycling operation during which all fuel and electrical energy are shut-olf.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing, wherein a schematic View of'a safety control and ignition system embodying the invention is shown.

Referring more particularly to the drawing, a main burner l is supplied with fuel by a. main fuel pipe l2 in which the flow of fuel is under the separate control of a main control device, shown as a valve or cock I4, and of a safety valve I8 forming an electromagnetic control means. The safety valve I8 is provided with a partition i8 having a valve seat 28 with an opening 22 therethrough controlled by a reciprocable valve member 24. A coil spring 28 is operable between the valve member 24 and a wall of the safety valve I8 for biasing the valve member 24 toward the valve seat 28. 'I'he valve member 24 is provided on the side opposite the coil spring 28 with (Cl. 15S-117.1)

a valve stem 28 which extends through the opening 22 to the exterior of the safety valve I8.

The electromagnetic operator for the safety valve I8 comprises a support 38 through which a reset stem 3l extends in .axial alignment with the projecting end of the valve stem 28 to which it is connected. The reset stem 3l terminates in a button 32 supporting `a second coil spring 34 which extends to the adjacent support 30 and cooperateswith the coil spring 28 in its biasing action;

The support 30 carries a horseshoe magnet 38 having a movable armature 38 engageable with the pole faces thereof and supported on the valve stem 28 for alternative engagement with a pair of spaced collars 48 and 4I formed thereon. When pressure is applied to the button 32 to move the valve stem 28 and the valve member 24 against the bias of the springs 28 and 34 the armature 38 will be engaged by the collar 4I and reset against the pole faces of the magnet 38. I

The safety valve I8 also controls the flow of fuel to a pilot burner 44 located in proximity to the main burner Ill. The pilot burner 44 is con-1, nected to the safety valve I8 by a conduit 48 whichcommunicates with an aperture 48 in the partition I8 to receive fuel from the valve seat vopening 22 when the valve member 24 is disengaged Afromrits seat. In order that ow of fuel to the main burner I8 may be prevented during the resetting operation while such ow is permitted to .the pilot burner 44, the valve stem 28 carries a closure member 80 for the underside of the valve seatopening 22. Thus, when the collar 4| is 'engaged with the armature 38 during the resetting operation the closure member 80 is simultaneously engaged with theunderside of the valve seat opening 22 for the described purpose. will be apparent that the closure member could b e dispensed withvand the resetting operation could be conducted while fuel flows simultaneously in both the main fuel pipe l2 and the pIIot conduirait.

A thermocouple 82 is located in proximity to the llame of the pilot burner 44 to be heated thereby. The magnet 38 is .adapted to be en ergized by the current generated by the thermocouple .52 suiiiciently to hold the amature 38 against the pole faces of the magnet 38 upon completion of the resetting operation. Hence, a suitable coil or winding 84 is provided for the mag- 'net 38 and connected in circuit with the thermocouple 52 by wires 88 and 88.

The reset stem 3| is adapted to be moved inwardly against .thebias of the springs 34 and 28 by electrically operable means now to be described. This means comprises a transformer ,88 combined with an electromagnetically operatcdplung-` er 82 which is positioned in axlalalisnment with the reset stem 8l. 'I'he plunger 82 is adapted to be moved into operative engagement with the lbutton 82 when the primary coil 84 of the transformer 88 is energized. The plunger 82 is biased away from the button 82 by a coil spring 88 extending between the transformer 88 and a head 88 formed on the end of the plunger 82 opposite that which engages with the reset stem 8i. Associated with the primary coil 84 is a secondary coil 8l connected in circuit with an electric igniter 88 for the pilot burner 44 by means of the wires 'I8 and l2. It will be apparent that the safety valve I8 and its associated operating magnet 88 together with the transformer 88 could be combined in a unitary construction and the elements have been shown schematically in the drawing for illustrative purposes without intending any limitation to the exact form shown.

The primary coil 84 of the transformer 88 is connected to a source of electrical energy by wires 14 and 18 under control of a main switch 18. The main switch 18 may be manually operated, either separately from the operation of the main fuel cock i4 or combined therewith. Moreover, it will be apparent that the switch 18 could be thermostatically operated independently of the main fuel cock' I4 or a combined main valve, thermol static valve and electric switch such as disclosed in Weber Patent No. 2,276,751, March 17, 1942, could be employed.

Additional switching means for controlling the transformer 88 are provided in the form of contacts 88, 82 adapted to open and close the circuit thereof by operation of a switch 84 with which these contacts are associated. Preferably, the switch 84 is of the snap-action type as indicated in the drawing and is arranged for operation by a .thermally responsive means, such as the bimetal operator 88 positioned adjacent thereto. An electric heater 88 in the form of a coil is associated with the bimetal 88 for operating the switch 84 to open the contacts 88-82 when the bimetal 88 is heated. When the bimetal 88 is cold the contacts 88-82 are closed in the circuit of the wires 18 and 14.

The heater 88 of .the bimetal switch 84 is connected in shunt with the contacts 80-82 by a wire 90 connected at one end to the wire 14 and the other to one end of the coil 88; a wire 82 connected at one end to the opposite end of the coil 88 and at the other end lto a contact 84 which is carried by the armature 88 and is movable therewith into engagement with a stationary contact 88 carried on the support 30; and a wire 88 connected at one end to .the contact 88 and at the opposite end to the wire 18 to complete the shunt circuit.

In the operation of the device, assuming coldstart conditions, the main fuel cock i4 is opened to admit fuel to the safety valve I8 and the main switch 'I8 is closed to energize the transformer circuit. Since the bimetal switch 84 is closed under the cold-start condition, the primary winding 84 of the transformer 88 is connected directly to the power supply and is energized. This causes the plunger 82 to be picked up and the igniter 88 to be energized by the secondary 81.

In its pick-up position the plunger 62 engages the button 82 0f the reset stem 8| and forces the armature 88 against the pole faces of the magnet 88. In this armature position the contacts 84-88 are closed. Moreover, the valve member 24is disengaged from the valve seat 28 and the closure member 88 interrupts the ilow of fuel through the valve aeat opening 22 to the main burner I8. The passage of fuel to the pilot burner 44 is permitted through the conduit 48 due to the aperture 48 provided in the valve seat opening 22. The fuel flowing from the pilot burner 44 is ignited by the igniter 88 and thel hermocouple 82 becomes heated by the resulting am. i

The heating of the thermocouple 82 is accompanied by a simultaneous heating of the heater 88 due to the closing of the contacts 84-88 by operation of the armature 88. It is apparent that in normal operation the bimetal switch 84 is adjusted so that the time for the bimetal op erator 88 to become heated sumcie'ntiy to open the switch 84 is longer than the time required for the thermocouple 82 to become heated sumciently to generate current and cause the armature 88 to be retained against the pole faces of the magnet 36. When the bimetal switch 84 is opened by the operation of the heated bimetal 88 .the circuit controlled thereby is discontinued and the transformer 88 becomes deenergized. Thus, the force of the plunger 82 against the reset stem 8| is removed and the coil springs 28 and 84 would serve to disengage the armature 88 from the pole faces of the magnet 88 unless the thermocouple 82 is generating sumcient current in the coil 84 to cause retention of the armature in attracted position.

With the armature 88 held against the pole faces of the magnet 38 by the energy supplied by the thermocouple 82 and the plunger 82 no longerA exerting force on the reset stem 8|, then the only movement which occurs ln response to the bias of the coil springs 28 and 84 is lost motion permitted by the spacing of the collars 48 and 4i. Such movement causes the collar 48 to become engaged with the armature 88 and -the collar.

.to be spaced therefrom with the result that the closure member 58 becomes disengaged from the partition I8. Fuel is now permitted to flow through the valve seat opening 22 to the main burner ill to be ignited by the flame from the pilot burner 44. The control is then in steady state running condition.

During the steady state operation the only external power required by the system is that supplied to the heater coil 88 through the shunt circuit established by closed contacts 84-88. The energization of this heater coil 88 is required at this time to maintain the switch 84 in its open position and to cooperate in the recycling procedure in case oi' flame failure. In the event that flame failure occurs, the thermocouple 52 would cool olf and the mainbumer fuel would escape until the energy generated by the thermocouple 52 became reduced sufficiently to allow the armature 88 to be released. Engagement of thearmavture 38 with the collar 4l would then occur and the bias of the coil springs 28 and .34 would cause closure of the valve member 24. A complete shutoff of all fuel :to the main burner I8 and the pilot burner 44 occurs when the valve member 24 is closed. As the contacts 84-88 are opened by movement of the armature 88 to released position, the heater 88 becomes deenergized and a purge period ensues during which all fuel and external power is shut off. This purge period is equal to the time required for the bimetal 88 to cool oil sumciently to cause closure of the contacts 88-82 of the switch 84.

assigns The recycling operation occurs immediately following the purge period due to this closing of the contacts -82 of the switch 8l and the consequent energizing of the primary 6l of the transformer 60. 'I'he sequence of operations is then the same as that described in the case of a cold start and further description is deemed unnecessary. The operation of the bimetal switch 48l under cold-start and recycling conditions is silent and a comparatively noiseless control has been provided. The main burner fuel is ignited within a few seconds of turning on the system which is advantageous in oven and broiler installations. In steady state operationl there is no `possibility of disturbances due to line voltage variation or large starting currents of other equipment connected to the same supply line as a separate thermo-electric current supply is relied upon.

While a relatively simple safety control and ignition system for gaseous fuel burners has been described and shown, it will be apparent that many changes can be made in the arrangement and combination of parts and in the detailsy of construction herein disclosed within the scope of the appended claims without departing from the spirit of the invention.v

claim:

l. A safety control system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination, electromagnetic control means biased to a fuel flow preventing position, electromagnetic reset mearrs for overcoming said bias and resetting said control means in a fuel now permitting position, an energizing circuit including the source and said reset means, means responsive to the presence of a name at the pilot burner for energizing said con -trol means suiilciently to hold the same in said fuel flow permitting position thereof, switching means having contacts for opening and/'closing said circuit, thermally responsive means adapted when heated for operating said switching means to open said contacts, an electric heater for said thermally responsive means, and means for establishing another energizing circuit including the source and said heater upon completion of said resetting operation.

2. A safety control system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination, electromagnetic control means biased to a fuel ow preventing position, electromagnetic reset means for overcoming said bias and resetting said control means in a fuel iiow permitting position, an energizing circuit including the source and said reset means, means responsive to the presence of a flame at the pilot burner for energizing said control means sufiiciently to hold the same in said fuel oW permitting position thereof, switching means having contacts for opening and closing said circuit, thermally responsive means adapted when heated for operating said switching means to open said contacts, an electric heater for said thermally responsive means, and means responsive to resetting operation of said reset means for establishing another energizing circuit including the source and said heater and in shunt with said contacts, said other circuit maintaining said heater in energized condition While said control means is held in said ilow permitting position.

3. A safety control system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination, electromagnetic control means biased to a fuel flow preventing position, electromagnetic reset means for means in a fuel ilow permitting position, an energizing circuit including the source and said reset means, a thermocouple located to be heated :by a llame at the pilot burner for energizing said control means suillciently to hold the same in said fuel flow permitting position thereof, switching means having contacts for opening and closing said circuit. thermally responsive means adapted when heated for operating said switching means to open said contacts, an electric heater for said thermally responsive means adapted to cause said operation thereof subsequent to energization of said control means by said thermocouple, a second energizing circuit including the source and said heater and in shunt with said contacts, and asecond switching meansy having contacts for opening and closing said second circuit. said second switching means being responsive to resetting operation of said resetmeans for closing the last said contacts.

4. A safety control and ignition system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination, an electric igniter for the pilot burner, electromagnetic control means biased to a fuel flow preventing position, electromagnetic reset means for overcoming said bias and resetting said control means in a fuel flow permitting position, an energizing circuit including the source, said igniter and said reset means, means responsive to the presence of a flame at the pilot burner for energizing said control means sufliciently to hold the same in said fuel flow permitting position thereof, switching means having contacts for opening and closing said circuit, thermally responsive means adapted when heated for operating said switching means to open said contacts, an electric heater for said ,thermally responsive means, and means for establishing another energizlng circuit including the source and said heater upon completion of said resetting operation.

5. A safety control system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination, electromagnetic control means biased to a fuel ilow preventing position, reset means including a transformer having a plunger for overcoming said bias and resetting said control means in a fuel flow permitting position, an energizing circuit including the source and said reset means, means responsive to the presence of a flame at the pilot burner for energizing said control means sumciently to hold the same in said fuel now permitting position thereof, switching means having contacts for opening and closing said circuit, thermally responsive means adapted when heated for operating said switching means to open said contacts, an electric heater for said thermally responsive means, and means f or establishing another energizing circuit including the source andand said reset means, an electric igniter for the pilot burner connected to said coil, means respon- Aovercoming said bias and resetting said control sive to the presence of a ilame at the pilot burner for energizing said control means sufficiently to hold the same in said fuel ilow permitting position thereof, switching means having contacts for opening and closing said circuit, thermally remonsive means adapted when heated foroperating said switching means to open said contacts, an electric Aheater for said thermally responsive means. and means for ,establishing another energizing circuit including the source and said heater upon completion of said resetting operation.

7. A safety control and ignition system for fuel burners having main and pilot burners and a source of electrical energy, comprising in combination. electromagnetic control means having an amature and biased to a fuel ilow preventing position. reset means including a transformer having a coil and a plunger operatively engageable with said armature for overcoming said bias and resetting said control means in a fuel ow permitting position. an energizing circuit including the source, said coil and said reset means. an electricigniterforthepilotburnerconnectedtosaid coil. a thermocouple located. to laml heated by a flame at the pilot burnerfor energizing vsaid control means sumciently to hold the same in said fuel ilow permitting position thereof, switching means having contacts for opening and closing said circuit. thermally remonsive means adapted when-heated for operating said switching means to open said contacts, an electric heater for said thermally responsive means and adapted to cause said operation thereof subsequent to energlzation of said control means by said thermocouple, a second energizing circuit including the source and said heater and in shunt with said contacts, and a second switching means having contacts operable by said armature ior opening and closing said second circuit, said second switching means being responsive t'o resetting operation of said reset means for closing the last said contacts.

CHARLES K. STROBEL. 

